A receiver is an apparatus that can realize electro-acoustic energy conversion, which is widely used in electronic terminal devices such as mobile phones, telephones and so on. The conventional receiver construction generally comprises a magnetic circuit system, a vibration system, and an external housing which accommodates the magnetic circuit system and the vibration system. The external housing generally comprises an upper housing, a middle housing and a lower housing adapted with each other. The vibration diaphragm of the vibration system divides the receiver into a front acoustic cavity and a rear acoustic cavity, wherein the front acoustic cavity is generally a space defined by the diaphragm, the middle housing and the upper housing, and the rear acoustic cavity is generally a space defined by the diaphragm, the middle housing and the lower housing, furthermore, the rear acoustic cavity is generally provided with a sound outlet hole communicating the cavity with outside environment.
In the configuration of the existing receiver, the rear sound hole arranged in the rear sound cavity is designed to be open to outside, and this configuration enables the vibration system to directly communicate with the outside environment, resulting in impurities such as small particles, fibers and dust in the outside environment easily falling into the rear sound cavity in production process, so that when a product of the receiver operates, the voice coil and the vibration diaphragm easily collide with impurities entering interior of the receiver, resulting in product performance degradation. In view of this, it is necessary to improve current design of the rear sound hole in order to avoid a technical problem that the above-described impurities easily fall into the rear sound cavity.